Air-cooled pump assembly for hydraulic fluid and the like



Aug. 7, 1962 c. w. TYDEMAN 3,043,119

AIR-COOLED PUMP ASSEMBLY FOR HYDRAULIC FLUID AND THE LIKE Filed June 2, 1961 5 Sheets-Sheet 1 INVENTOR. CIA/125N635 M TYDEMA/v A 7' TO/PNE Y5 Aug. 7, 1962 c. w. TYDEMAN 3,043,119

AIR-COOLED PUMP ASSEMBLY FOR HYDRAULIC FLUID AND THE LIKE Filed June 2, 1961 3 Sheets-Sheet 2 4 2 3 w m M Wm-HIM o %==l rl Q... 0 m I, a ms a 5 M 1 0Q Q 8 Q Q 4 0 Q a k m m A a F /l wl v 4 ll M 6 fie. 5,

IN VEN TOR. CLARENCE M TYDEMA/V 1 TTO/PN E Y5 Aug. 7, 1962 c. w. TYDEMAN 3,048,119

AIR-COOLED PUMP ASSEMBLY FOR HYDRAULIC FLUID AND THE LIKE Filed June 2, 1961 3 Sheets-Sheet 3 r v66 M 25 T /68 ms 56 46 INV EN TOR.

CLARENCE M TYDEM/IN A TTO/PNE Y5 United States Patent Office 3,048,! 19 Patented Aug. 7, 196 2 3,048,119 AIR-COOKED PUMP ASSEMBLY FOR HYDRAU- LIC FLUID AND THE LIKE Clarence W. Tydeman, Timnath, Colo., assignor to Tydeman Machine Works, Inc., Redwood City, Calif., a corporation of California Filed June 2, 1961, Ser. No. 114,386 11 Claims. (Cl. 103-118) This invention relates to hydraulic pumps and, more specifically, to air-cooled pumps of a type adapted to deliver hydraulic fluid to an operating unit at a substantially constant temperature and pressure. I

In my copending application Serial Number 101,297 filed April 6, 1961, I disclose an improved hydraulicallyoperated tracer assembly for engine and turret lathes that is capable of reproducing the contoured edge of a template on a workpiece to tolerances of plus or minus 0.0001 inch. In order for this high degree of accuracy to be attained, however, it is absolutely necessary that the hydraulic fluid which forms the operative connection between the stylus or feeler of the tracer unit and the toolholding quill of the cutter unit be delivered thereto at a relatively high pressure and at a nearly constant ambient temperature; otherwise, the degree of precision that the assembly is capable of producing becomes impossible to realize. In fact, this same thing is true of most, if not all, high-precision hydraulically-operated machinery.

Now, it is well known that hydraulic fluid can be pumped to an operatingunit at a nearly constant pressure and relatively low uniform temperature by utilizing any one of a number of different types of refrigeration units either directly associated with the pump or connected into the feed lines intermediate the pump and operating unit. While this approach to the problem must be con- 'sidered effective to produce the desired end result, namely, holding the temperature of the fluid nearly constant, it has a number of serious drawbacks that make it more or less impractical. For example, the size and weight of the refrigeration unit required to handle the flow of fluid results in apparatus that cannot be considered portable in the common sense of the term. In addition to the problem of bulk, the operating costs are likelyto be rather high to say nothing of the substantial increase in initial expense. As a result, most machine shops prefer some type of air-cooled pump even though to use one of the prior art designs often means sacrificing a significant amount of the accuracy the hydraulically-operated machine tool connected thereto is capable of producing.

The need for some type of cooling apparatus becomes readily apparent when it is realized that a gear pump operated by a one-half horsepower motor to deliver fluid at a rate of less than a gallon per minute and a pressure of about 500 p.s.i. will result in the fluid coming to a boil within the period of approximately one-half hour. This, of course, is an intolerable situation and means must be provided for holding the oil temperature down to a Workable level.

The prior art attempts to design an air-cooledhydraulic pump effective to maintain a fluid pressure of the order of 500 p.s.i. at a temperature not to exceed approximately 125 F. have met with little success in terms of a compact, portable and inexpensive unit. Some of them, while effective to hold the temperature of the fluid to a useable maximum, permit variations over a rather wide range somewhat dependent upon whether the machine tool is being operated or the fluid is merely circulated by-passing the operating unit. Although the maximum temperature is not a critical factor in such a unit, the fluctuations therein are, giving rise toerratic and unpredictable operation of the machine tool.

It is, therefore, the principal object of the present invention to provide a novel and improved air-cooled pump for hydraulic fluid and the like.

A second objective is the provision of a pump of the class described which is operative to maintain the temperature of the fluid nearly constant at about 20 F. above ambient temperature over extended periods of operation.

Another object of the invention which for-ms the subject matter hereof is to provide a lightweight portable aircooled gear pump assembly.

Still another objective is to provide a pump housing having an improved radiator design.

An additional object of the invention herein disclosed is the provision of a circulating gear pump assembly that includes a non-chattering check valve of unique construction.

Further objects are to provide an invention of the class aforementioned which is relatively inexpensive, versatile, virtually trouble-free, compact, adaptable for use in a wide variety of fluidpumping applications and decorative in appearance.

Other objects will be in'part apparent and in part pointed out specifically hereinafter in connection with the description of the drawings that follows, and in which:

FIGURE 1 is a diametrical section showing the aircooled gear pump forhydraulic fluids of the present invention; s

FIGURE 2 is a fragmentary sectional detail taken along line 2-2 of FIGURE 1 illustrating the fluid delivery passage in the radiator together with the overflow passage back to the sump;

FIGURE 3 is a fragmentary section taken along line 3--3 of FIGURE 2 showing a different view of the overflow passage;

:FIGURE 4 is a horizontal section through the radiator taken along line 4-4 of FIGURE 1;

FIGURE 5 is a vertical section through the radiator taken along line 5-5 of FIGURE 4;

I FIGURE 6 is a top plan view showing the ring that supports the cap or cover for the fan and radiator;

of FIGURE 1 showing the gear pump slightly enlarged; and

FIGURE 8 is a fragmentary sectional detail to an enlarged scale illustrating the pressure regulator assembly, portions of the valve element having been broken away to expose the interior construction.

Referring now to the drawings for a detailed description of the air-cooled pump of the present invention which has been designated broadly by numeral 10, and particularly to FIGURE 1 for this purpose, it will be seen to include a sump or fluid reservoir 12 that provides a base on top of which rests a coverplate 14 supporting a gear pump 16 on the underside thereof, a radiator 18 providing a housing for motor 20 that operates both the gear pump 16 and fan 22, and a cap or cover 24 attached to the top of the radiator by means of supporting ring 26'. Fluid reservoir 12 has an open-topped hollow cylindrical configuration, the wall portion 28 of which is provided with a fill opening 30, an opening 32 for exhaust line 34, and an opening receiving tube 36 by which fluid from the sump or reservoir is delivered to thermometer 38. An elbow fitting 40 is attached within the fill opening 30 and provided with a plug 42 which keeps dust and dirt out of the fluid which might otherwise cause faulty operation of the hydraulically-controlled mechanism receiving fluid from the pump. The plug is, of course, only removed when the fluid is changed or replenished.

The upper edge of the wall portion 28 of the reservoir 12 is, in the particular form shown, provided with an integrally-formed inturned flange 44 to which is bolted or otherwise attached a coverplate 14 that carries the gear pump 16 suspended from the underside thereof as well as providing structure containing the lower portions of the fluid delivery passage 46 and overflow passage 4-8. The reservoir is filled with hydraulic fluid to a level which at least submerges the lower end of pump intake passage 56.

Coverplate 14 comprises a circular disk having a cupshaped cavity 52 in the center thereof that contains a centrally-located opening 54 in its bottom portion 56 adapted to pass the shaft 58 by means of which the pump 16 is driven. The edge of the disk-shaped coverplate is bolted to the inturned flange 44 of the reservoir forming a fluid-tight seal therewith. The radiator 18 is, in turn, bolted to the coverplate and centered with respect thereto by means of interlocking circular rib portions 60 and 62. integrally-formed boss 64 adjoining the cupshaped cavity of the coverplate on the outside thereof contains both fluid delivery passage 46 and overflow passage 43, the precise location and arrangement of which will be set forth in greater detail presently in connection with the description of FIGURES 2 and 3.

Now, in connection with FIGURES 1 and 7, it can be seen that pump 16 is of the common gear-type having an intake passage 56 opening onto the underside thereof which is enclosed by a filtering screen 66. The fluid taken into the intake passage is delivered to the meshed gear elements 68 and 70 that are journalled for rotation within figure-eightshaped cavity 72. One of the gear elements 70 is mounted on a stub shaft 74 for rotation therewith while the other gear element 68 is mounted on shaft 58 that is connected to the motor shaft 76. The entire pump unit 16 is, therefore, eccentrically located on the underside of the bottom portion 56 of the cup-shaped cavity 52 in coverplate 14 to place shaft 58 in axial alignment with the centrally-located motor shaft 76.

Rotation of the gear elements 68 and 70 within cavity 72 in the direction of the arrow in FIGURE 7 picks up fluid from the intake passage and delivers same to delivery passage 46 provided in the integrally-formed boss 64 carried by the coverplate 14 under pressure. The particular manner in which delivery passage 46 is constructed by drilling intersecting radial and vertical passages from the exterior surfaces of the coverpiate, pump housing and radiator and, thereafter, plugging the surface openings, is well known in the art forming no part of the present invention; therefore, it will not be described in detail although readily apparent from an examination of FIGURE 1. I

The construction of the radiator 18 can best be seen in connection with FIGURES 1, 4 and 5 to which reference will be made. As aforementioned, interlocking annular ribs 69 and 62 on the bottom 78 of the radiator and top of coverplate 14 center these elements with respect to one another while fasteners 80 maintain the assembled relation therebetween. The bottom 78 of the radiator includes a centrally-located opening 82 through which the motor shaft 76 passes into the cup-shaped cavity 52 in the coverplate where it is attached to shaft 58 of the pump by means of shaft coupling 84. An upstanding annular rib 86 surrounds central opening 82 and is provided with an annular shoulder 88 projecting inwardly therefrom on which shaft bearing 90 is supported.

A hollow cylindrical wall portion 92; extends upwardly from the bottom 78 of the radiator defining a housing for electric motor 26 that is encased therein. In the particular form shown, the stationary field poles 94 of the motor that carry the field winding or coil 96 are supported on the shoulder 98 defined by an inwardly extending annular rib 1W placed on the inside surface of hollow cylindrical Wall portion 92. The motor shaft 76 is provided with a shoulder 102 that rests on the inner race of thrust bearing 90 supporting the armature 1% for rotation Within the field coil. At the juncture of the hollow cylindrical wall portion 92 with the bottom 78 of the radiator 18, a series of exhaust ports 166 are provided for purposes of dissipating the heat generated by the motor. Fan blade 22 mounted on the upper end of motor shaft 76 directs air down through openings 137 in supporting ring 26 and over the motor thus forcefully exhausting the heat generated by the motor from the radiator through openings 166.

An annular cooling chamber 168 surrounds the hollow cylindrical wall portion 92 of the radiator defined by radial flange 110, downwardly and outwardly sloped flange 112, and connecting wall portion 114 that joins the free edges of these flanges which are cast integrally with wall portion 92 that provides the fourth wall of the chamber. As shown, the fluid cooling chamber is generally trapezoidal in vertical section with the inclined flange 11?. positioned directly in the path of the air circulated downwardly from the periphery of the fan 22 through openings 116 in the support ring 26 and into the convergent air space left between the exterior surface of the radiator and the interior surface of the annular skirt 118 of cap 24. Air flowing over inclined flange 112 and connecting wall portion 114 of the radiator provides for primary cooling of the fluid being circulated within chamber 108 as it carries away the heat through the annular gap 120 left between the adjacent surfaces of the radiator and cap or cover 24. Some secondary cooling is achieved from the air forced by the fan past the motor along hollow cylindrical wall portion 92 and out past radial flange 110 although this lflow is primarily for the purpose of carrying 01f the heat of the motor before it can heat up the fluid in the adjacent cooling chamber appreciably.

An integrally-formed boss 122 projects into cooling chamber 108 and contains the delivery passage 46, overflow passage 48, branch passage 124 that leads to the hydraulically-operated machine tool or the like controlled by the pump mechanism, pressure-responsive valve assembly 126 along with the cavity 123 therefor, and passage 1% connecting the latter cavity into the cooling chamber of the radiator. A detailed description of these passages, their location and function will again be defined pending completion of the radiator, supporting ring 26 and cover 24.

From FIGURES 4 and 5 it is apparent that radiator 18 is preferably cast as a unitary structure from some metal, such as aluminum, which provides a good coefficient of thermal conductivity as well as being relatively lightweight yet strong. In a cast element such as radiator 18 containing an internal annular cooling chamber such as that numbered 108 within which the fluid circulates, it is, of course, necessary to provide a plurality of core holes 132 opening into the chamber from which the mold can be removed. As illustrated, three of these core holes are plugged with soft plugs 134 while the fourth contains a removable threaded plug 136 providing continued access to the cooling chamber for inspection and cleaning puroses.

FIGURES 1 and 6 show most clearly the construction of supporting ring 26 which comprises a centrally-located hub-forming portion 137 that houses the bearing 13% in which the motor shaft 76 is journalled, a plurality of spoke-like portions 140 extending radially outward from the hub-forming portion in angularly spaced relation to their point of attachment with outer ring portion 142, and an integrally-formed inner ring portion 144 interconnecting the spoke-like portions intermediate the hub portion and the outer ring portion. The interstices between the hub, spokes and ring portions define the openings 116 and 107 of the supporting ring, the location and function of which have already been described.

Inner ring portion .144 overlies the upper edge of the hollow cylindrical Wall portion 92 of the radiator and is attached thereto by suitable fasteners as indicated. The outer ring portion 142, on the other hand, engages the underside of shoulder 146 provided on the inner surface of the skirt .118 of cover 24.

Cover or cap 24'can only be seen in FIGURE 1 where it will be noted to have an open top covered by screen 148 which protects the fan 22 yet provides an air intake opening. The annular skirt 118 supports the screen in spaced relation above supporting ring 26 thus defining a cavity 150 in which the fan operates. The skirt 118 extends downwardly below ring 26 in spaced relation outside radiator 18 and directs the air from the fan along the inclined flange 112 of the latter to carry away the heat conducted therethrough from the fluid. An opening 152 is provided in the skirt of the cover adjacent the pressureresponsive Valve assembly 126 enabling the latter to be removed and serviced.

Having described in detail the several components of the air-cooled pump assembly with the exception of pressure regulator assembly 126 shown in FIGURE 8, reference will now be made to FIGURES 1, 2 and 3 for an explanation of the fluid-circulating and cooling systems. Ordinarily, the hydraulically-operated servo-system operating a machine tool or the like that is connected to the pump assembly of the present invention will operate only intermittently and require a good deal less than the full volumetric output the pump is capable of delivering. Thus, an efflcient by-pass system is absolutely necessary which will keep the fluid circulating while being cooled to maintain a relatively constant temperature. In this connection it should be noted that the fluid heats up the most when being circulated in the by-pass system rather than when it is being delivered to the servo-system in the operating circuit, the greatest temperature rise occurring as the fluid passes the pressure-responsive valve assembly in'the by-pass circuit. Also, it is mandatory that the fluid in the bypass system be maintained at a pressure at least equal to, and preferably considerably greater, than the maximum operating pressure of the operating circuit; otherwise, the

fluid would be by-passed continually and never be available for use in the higher pressure operating circuit. Accordingly,. the function of the pump is to maintain an excess of high pressure fluid available at a relatively constant temperature at all times to satisfy the operatin requirements of the servo-system.

Now, the fluid issuing from the pump under pressure passes in delivery passage 46 through boss 64 in the coverplate 14 for the reservoir up into boss 122 located inside the annular cooling chamber 108 in the radiator 18 where it opens the pressure-responsive valve assembly 126 and drops down through passage 130 into said annular chamber. As the fluid enters the cooling chamber and circulates therearound it is cooled by the air circulated by fan 22 passing over the walls bordering said chamber which conduct the heat away to the atmosphere. When the fluid level in chamber 108 reaches the top of overflow passage 48 (FIGURES 2 and 3) it drops back down through the radiator into the reservoir.

The effectiveness of the pump assembly can best be appreciated from the fact that when equipped with a pump delivering slightly less than a gallon per minute and the pressure regulator adjusted to maintain the fluid pressure at about 500 p.s.i., the temperature of the fluid remained relatively constant at approx mately above ambient temperature even though all of the fluid was by-passed continuously for a period of eight hours, the normal working day.

The operating circuit of the pump assembly comprises merely branch passage 124 located in the boss 122 of the radiator which opens into delivery passage 46 upstream The outlet of this' that of the bypass circuit and usually on an intermittent basis.

Finally with reference to FIGURES l and 8 the novel and improved pressure-responsive valve assembly 126 especially suited for use in the instant air-cooled pump unit will be described. Valve cavity 128 opens onto the exterior of boss 122 of the radiator and, as shown, extends inward essentially radially to intersect both passage 130 and delivery passage 46. The inner extremity of cavity 128 is tapered at its point of connection with delivery passage 46 to provide a frusto-conical seat 156 located upstream of the intake end of passage 130. A truncated right conical valve element v158 mates with seat 156 providing a fluid-tight seal therewith when biased into closed position by compression spring 160 located in cavity 128 between said valve element and plug 162. The intermediate portion of cavity 128 is preferably threaded internally as indicated to receive the threaded section 164 of the plug. The outer extremity of the valve cavity is smooth-bored to form a fluid-tight seal with O-ring 166 provided in annular groove 168 at outer end of plug 162. Threaded adjustment of the plug in the valve cavity varies the prel-oad compression on spring 160 thus regulating the fluid pressure required to unseat valve element 156.

Valve element 156 is constructed to provide a transverse passage 178 opening onto the conical surface at diametrically opposed points and a longitudinal passage 1'72 interconnecting the transverse passage 170 with delivery passage 46. When seated as shown in FIGURES 1 and 8, the outlets of the transverse passage 170 are, of course, closed against the frusto-conical surface of the valve seat thus preventing the movement of fluid into passage 130. When, however, the fluid-pressure in delivery passage 46 exceeds the opposing force applied by spring 160, the valve element will move off its seat allowing fluid to pass from the delivery passage 46 into passage 130.

If passages and 172 were eliminated from the valve element 158 it would function much in the same manner as a ball check valve used as a pressure-responsive system; however, experience with the use of ball check valves in such a high pressure fluid system has shown them to be unsatisfactory from the standpoint that they develop a chatter at certain critical fluid pressures which produce I erratic operation due to fluctuations in the line pressure leading to the servo-mechanism. The instant valve mechanism, on the other hand eliminates this chattering problem through the use of passages 17) and 172. The truncated conical valve element is, of course, required to maintain longitudinal passage 17.2 aligned with the discharge end of delivery passage 46 which would not be possible with a spherical valve element.

Having thus described the several useful and novel features of the air-cooled pump assembly of the present invention it will be apparent that the many worthwhile objectives for which it was designed have been achieved. Although but a single specific embodiment of the invention has been illustrated and described in the accompanying drawings, I realize that certain changes and modifications therein may well occur to those skilled in the art within the broad teaching hereof; hence, it is may intention that the scope of protection afforded hereby shall be limited only insofar as said limitations are expressly set forth in the appended claims.

What is claimed is:

1. An air-cooled pump for hydraulic fluid and the like which comprises: an open-topped reservoir having an opening in a wall portion thereof adapted for connection to an exhaust line returning fluid thereto from an operating unit; a coverplate secured to the open top of the reservoir in fluidtight sealed relation, said coverplate including a fluid delivery passage and an overflow passage; a pump supported on the underside of the coverplate within the reservoir in position to draw fluid therefrom and deliver same under pressure to the delivery passage; a radiator mounted atop the coverplate in fluid-tight we-at."

ao ae, 1 19 F sealed relation thereto and including a centrally-located open-topped hollow cylindrical wall portion defining a motor housing, a continuous annular cooling chamber surrounding the motor housing, a boss located within the annular cooling chamber, said boss containing a valve socket connected to receive fluid from the delivery passage in the coverplate, a branch outlet passage connected to receive fluid from the delivery passage upstream of the valve socket for delivery to the operating unit, and a passage interconnecting the annular cooling chamber with the valve socket downstream of the latters connection into the delivery passage, and exhaust ports in the base of the motor housing; a motor mounted in the hollow cylin drical wall portion of the radiator and operatively connected to the pump through the coverplate; a fan operatively connected to the motor for rotation above the radiator in a direction to circulate air downwardly across both the inside and outside walls of the annular cooling chamber to cool the fluid contained therein, said fan also directing air over the motor and out the exhaust ports in the motor housing; support-forming means attached to the top of the radiator underneath the fan journalling the motor shaft; a cap attached to the support-forming means in position to cover the fan, said cap having an open top adapted to admit air to the fan and an annular skirt encircling the radiator in spaced relation to the annular cooling chamber therein; and, pressure-responsive valve means located in the valve socket between the outlet of the delivery passage and the inlet of the passage connecting said valve socket into the annular cooling chamber of the radiator, said valve means being operative to open at a predetermined pressure in excess of that required to actuate the operating unit connected to receive fluid from the branch passage and deliver same to the annular cooling chamber where it is cooled before entering the overflow passage for return to the reservoir, and said valve means being operative to close shutting off the supply of fluid to the cooling chamber when the operating unit is receiving fluid from the pump through the branch passage.

2. The air-cooled pump as set forth in claim 1 in which the valve socket terminates at its inner end where it opens into the delivery passage in a frusto-conical valve seat located ahead of the intake end of the passage interconnecting said valve socket with the cooling chamber, and

- in which the pressure-responsive valve means comprises a truncated conical valve elements shaped to fit the trustsconical seat forming a fluid-tight seal therewith, a plug closing the outer end of the valve socket, and a compres sion spring connected between the plug and valve element biasing the latter into closed position.

3. The air-cooled pump as set forth in claim 1 in which the cooling chamber is defined by the hollow cylindrical wall portion of the radiator, a substantially radial flange encircling said hollow cylindrical wall portion on the outside thereof above the exhaust ports, a downwardly and outwardly flared flange encircling the cylindrical wall 3 portion spaced above the radial flange and a second hollow cylindrical wall portion spaced outwardly of the first hollow cylindrical wall portion interconnecting the radial and inclined flanges to form a fluid-tight chamber having a generally trapezoidal vertical cross section.

4. The air-cooled pump as set forth in claim 1 in which passage interconnecting the valve socket. with the cooling chamber is located to provide a gravity drain therebetween.

5. The air-cooled pump as set forth in claim 1 in which the inlet end of the overflow passage in the cooling chamber is located to maintain the latter chamber substantially full of fluid.

6. The air-cooled pump as set. forth in claim 1 in which the adjacent surfaces of the skirt and cooling chamber converge toward the exhaust opening defined therebetween.

7. The air-cooled pump as set forth in claim 1 in which the support-forming means comprises a centrally-located hub portion journalling the motor shaft, a plurality of spokes radiating from the hub portion, an intermediate ring portion interconnecting the spokes and cooperating 'therewith and with the hub portion to define openings positioned to admit air circulated by the fan to the interior of the motor housing, said intermediate ring portion being attached to the hollow cylindrical wall portion of the radiator, and an outer ring portion interconnecting the entremities of the spokes to define therewith and with the intermediate ring portion a plurality of openings positioned to deliver air circulated by the fan into the space defined between the annular skirt of the cap and the cooling chamber of the radiator, said outer ring portion being attached to said skirt forming the support for the cap.

8. The air-cooled pumped as set forth in claim 2 in which the plug is adjustable within the valve cavity in a direction to vary the spring bias on the valve element for purposes of regulating the fluid pressure required to by-pa'ss fluid into the cooling chamber.

9. The air-cooled pump as set forth in claim 2 in which the valve element includes a transverse passage opening onto the conical surface thereof at at least one point and a longitudinal passage interconnecting the transverse passage with the truncated end of said valve element in position to receive fluid from the delivery passage in both open and closed positions.

1O. The air-cooled pump as set forth in claim 9 in which the plug is adjustable within the valve cavity in a direction to vary the spring bias on the valve element for purposes of regulating the fluid pressure required to bypass fluid into the cooling chamber.

11. The air-cooled pump as set forth in claim 9 in which the transverse passage opens onto the conical surface of the valve element at two substantially diametricallyspaced points.

No references cited. 

